Changes in respiratory muscle and lung function following marathon running in man

Wireless Sensing System Based on Biodegradable Triboelectric Nanogenerator for Evaluating Sports and Sleep Respiratory

The rapid growth of the Internet of Things and wearable sensors has led to advancements in monitoring technology in the field of health. One such advancement is the development of wearable respiratory sensors, which offer a new approach to real-time respiratory monitoring compared to traditional methods. However, the energy consumption of these sensors raises concerns about environmental pollution. To address the issue, this study proposes the use of a triboelectric nanogenerator (TENG) as a sustainable energy source. The electrical conductivity of the TENG is improved by incorporating chitosan and carbon nanotubes, with the added benefit of chitosan's biodegradability reducing negative environmental impact. A wireless intelligent respiratory monitoring system (WIRMS) is then introduced, which utilizes a degradable triboelectric nanogenerator for real-time respiratory monitoring, diagnosis, and prevention of obstructive respiratory diseases. WIRMS offers stable and highly accurate respiratory information monitoring, while enabling real-time and nondestructive transmission of information. In addition, machine learning technology is used for sleep respiration state analysis. The potential applications of WIRMS extend to wearables, medical monitoring and sports monitoring, thereby presenting innovative ideas for modern medical and sports monitoring.

A preliminary exploration of the regression equation for performance in amateur half-marathon runners: a perspective based on respiratory muscle function

This document presents a study on the relationship between physical characteristics, respiratory muscle capacity, and performance in amateur half-marathon runners. The aim of this study was to establish a preliminary predictive model to provide insights into training and health management for runners. Participants were recruited from the 2023 Beijing Olympic Forest Park Half-Marathon, comprising 233 individuals. Personal information including age, gender, height, weight, and other relevant factors were collected, and standardized testing methods were used to measure various parameters. Correlation analysis revealed significant associations between gender, height, weight, maximum expiratory pressure, maximal inspiratory pressure, and half-marathon performance. Several regression equations were developed to estimate the performance of amateur marathon runners, with a focus on gender, weight, maximum expiratory pressure, and height as predictive factors. The study found that respiratory muscle training can delay muscle fatigue and improve athletic performance. Evaluating the level of respiratory muscle capacity in marathon athletes is crucial for defining the potential speed limitations and achieving optimal performance. The information from this study can assist amateur runners in optimizing their training methods and maintaining their physical wellbeing.

Breathing a low-density gas reduces respiratory muscle force development and marginally improves exercise performance in master athletes

INTRODUCTION

We tested the hypothesis that breathing heliox, to attenuate the mechanical constraints accompanying the decline in pulmonary function with aging, improves exercise performance.

METHODS

Fourteen endurance-trained older men (67.9 ± 5.9 year, [Formula: see text]O2max: 50.8 ± 5.8 ml/kg/min; 151% predicted) completed two cycling 5-km time trials while breathing room air (i.e., 21% O2-79% N2) or heliox (i.e., 21% O2-79% He). Maximal flow-volume curves (MFVC) were determined pre-exercise to characterize expiratory flow limitation (EFL, % tidal volume intersecting the MFVC). Respiratory muscle force development was indirectly determined as the product of the time integral of inspiratory and expiratory mouth pressure (∫Pmouth) and breathing frequency. Maximal inspiratory and expiratory pressure maneuvers were performed pre-exercise and post-exercise to estimate respiratory muscle fatigue.

RESULTS

Exercise performance time improved (527.6 ± 38 vs. 531.3 ± 36.9 s; P = 0.017), and respiratory muscle force development decreased during inspiration (- 22.8 ± 11.6%, P < 0.001) and expiration (- 10.8 ± 11.4%, P = 0.003) with heliox compared with room air. EFL tended to be lower with heliox (22 ± 23 vs. 30 ± 23% tidal volume; P = 0.054). Minute ventilation normalized to CO2 production ([Formula: see text]E/[Formula: see text]CO2) increased with heliox (28.6 ± 2.7 vs. 25.1 ± 1.8; P < 0.001). A reduction in MIP and MEP was observed post-exercise vs. pre-exercise but was not different between conditions.

CONCLUSIONS

Breathing heliox has a limited effect on performance during a 5-km time trial in master athletes despite a reduction in respiratory muscle force development.

Respiratory muscle training in non-athletes and athletes with spinal cord injury: A systematic review of the effects on pulmonary function, respiratory muscle strength and endurance, and cardiorespiratory fitness based on the FITT principle of exercise prescription

BACKGROUND

Respiratory muscle training (RMT) has been recommended to mitigate impacts of spinal cord injuries (SCI), but the optimal dosage in terms of the frequency, intensity, time, and type (FITT principle) to promote health in SCI individuals remains unclear.

OBJECTIVE

To discuss research related to the effects of RMT on pulmonary function, respiratory muscle strength and cardiorespiratory fitness in athletes and non-athletes with SCI, presenting the FITT principle.

METHODS

We performed a systematic review. PubMed, Lilacs, Scopus, Web of Science, PEDro, SciELO and Cochrane databases were searched between 1989 and August 2018. Participants were athletes and non-athletes with SCI.

RESULTS

4,354 studies were found, of which only 17 met the eligibility criteria. Results indicated that RMT is associated with beneficial changes in pulmonary function and respiratory muscle strength and endurance among athletes and non-athletes, whereas no effect was reported for maximal oxygen uptake. It was not possible to establish an optimal RMT dose from the FITT principle, but combined inspiratory/expiratory muscle training seems to promote greater respiratory changes than isolated IMT or EMT.

CONCLUSION

The use of RMT elicits benefits in ventilatory variables of athletes and non-athletes with SCI. However, it remains unclear which RMT type and protocol should be used to maximize benefits.

Inspiratory muscle training at sea level improves the strength of inspiratory muscles during load carriage in cold-hypoxia

Inspiratory muscle training (IMT) and functional IMT (IMT_F: exercise-specific IMT activities) has been unsuccessful in reducing respiratory muscle fatigue following load carriage. IMT_F did not include load carriage specific exercises. Fifteen participants split into two groups (training and control) walked 6 km loaded (18.2 kg) at speeds representing ∼50%V̇O_2max in cold-hypoxia. The walk was completed at baseline; post 4 weeks IMT and 4 weeks IMT_F (five exercises engaging core muscles, three involved load). The training group completed IMT and IMT_F at a higher maximal inspiratory pressure (P_imax) than controls. Improvements in P_imax were greater in the training group post-IMT (20.4%, p  = .025) and post-IMT_F (29.1%, p  = .050) compared to controls. Respiratory muscle fatigue was unchanged (p  = .643). No other physiological or subjective measures were improved by IMT or IMT_F. Both IMT and IMT_F increased the strength of respiratory muscles pre-and-post a 6 km loaded walk in cold-hypoxia. Practitioner Summary: To explore the interaction between inspiratory muscle training (IMT), load carriage and environment, this study investigated 4 weeks IMT and 4 weeks functional IMT on respiratory muscle strength and fatigue. Functional IMT improved inspiratory muscle strength pre-and-post a loaded walk in cold-hypoxia but had no more effect than IMT alone. Abbreviations: ANOVA: analysis of variance; BF: breathing frequency; CON: control group; EELV: end-expiratory lung volume; EXP: experimental group; FEV₁: forced expiratory volume in one second; FiO₂: fraction of inspired oxygen; FVC: forced vital capacity; HR: heart rate; IMT: inspiratory muscle training; IMT_F: functional inspiratory muscle training; P_emax: maximal expiratory pressure; P_imax: maximal inspiratory pressure; RMF: respiratory muscle fatigue; RPE: rate of perceived exertion; RWU: respiratory muscle warm-up; SaO₂: arterial oxygen saturation; SpO₂: peripheral oxygen saturation; V̇E: minute ventilation; V̇O₂: rate of oxygen uptake.

A flow resistive inspiratory muscle training mask worn during high-intensity interval training does not improve 5 km running time-trial performance

Purpose

There is little evidence of the ergogenic effect of flow-resistive masks worn during exercise. We compared a flow-resistive face mask (MASK) worn during high-intensity interval training (HIIT) against pressure threshold loading inspiratory muscle training (IMT).

Methods

23 participants (13 males) completed a 5 km time trial and six weeks of HIIT (3 sessions weekly). HIIT (n = 8) consisted of repeated work (2 min) at the speed equivalent to 95% \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${\dot{\text{V}}}$$\end{document}V˙O₂ peak with equal rest. Repetitions were incremental (six in weeks 1, 2 and 6, eight in weeks 3 and 4 and ten in week 5). Participants were allocated to one of three training groups. MASK (n = 8) wore a flow-resistive mask during all sessions. The IMT group (n = 8) completed 2 × 30 breaths daily at 50% maximum inspiratory pressure (P_Imax). A control group (CON, n = 7) completed HIIT only. Following HIIT, participants completed two 5 km time trials, the first matched identically to pre-intervention trial (ISO time), and a self-paced effort.

Results

Time trial performance was improved in all groups (MASK 3.1 ± 1.7%, IMT, 5.7 ± 1.5% and CON 2.6 ± 1.0%, p < 0.05). IMT improved greater than MASK and CON (p = 0.004). Post intervention, P_Imax and diaphragm thickness were improved in IMT only (32% and 9.5%, respectively, p = 0.003 and 0.024).

Conclusion

A flow-resistive mask worn during HIIT provides no benefit to 5 km performance when compared to HIIT only. Supplementing HIIT with IMT improves respiratory muscle strength, morphology and performance greater than HIIT alone.

The effect of an Olympic distance triathlon on the respiratory muscle strength and endurance in triathletes

High-intensity exercise, marathons, and long distances triathlons have been shown to induce the fatigue of respiratory muscles (RMs). Never-theless, fatigue and the recovery period have not been studied in re-sponse of an Olympic distance triathlon (1.5-km swim, 40-km bike, 10-km run: short-distance triathlon). The aim of this study was to evaluate the RM fatigue induced by an Olympic distance triathlon. Nine male triath-letes (24±1.1 years) underwent spirometric testing and the assessment of RM performance. Respiratory function tests were conducted in sit-ting position. Spirometric parameters, maximal inspiratory and expirato-ry pressures, and RM endurance assessed by measuring the time limit were evaluated before (pre-T), after (post-T), and the day following the triathlon (post-T-24 hr). Residual volume increased: pre-T vs. post-T (P<0.002), maximal inspiratory pressure significantly decreased from 127.4±17.2 (pre-T) to 121.6±18.5 cmH₂O (post-T) (P<0.001) and returned to the pre-T value 24 hr after the race (125.0±18.6). RM endurance sig-nificantly decreased from 4:51±0:8 (pre-T) to 3:13±0:7 min (post-T, P< 0.001) and then remained decreased for 24 hr after the race from 4:51± 0:8 (pre-T) to 3:39±0:4 min 24 hr after (P<0.002). Both, strength and en-durance of inspiratory muscles decrease after Olympic distance triath-lon. Furthermore, the impaired of inspiratory muscle endurance 24 hr after the race suggested a slow recovery and persistence of inspiratory muscle fatigue.

Pulmonary and Respiratory Muscle Function in Response to Marathon and Ultra-Marathon Running: A Review

The physiological demands of marathon and ultra-marathon running are substantial, affecting multiple body systems. There have been several reviews on the physiological contraindications of participation; nevertheless, the respiratory implications have received relatively little attention. This paper provides an up-to-date review of the literature pertaining to acute pulmonary and respiratory muscle responses to marathon and ultra-marathon running. Pulmonary function was most commonly assessed using spirometry, with infrequent use of techniques including single-breath rebreathe and whole-body plethysmography. All studies observed statistically significant post-race reductions in one-or-more metrics of pulmonary function, with or without evidence of airway obstruction. Nevertheless, an independent analysis revealed that post-race values rarely fell below the lower-limit of normal and are unlikely, therefore, to be clinically significant. This highlights the virtue of healthy baseline parameters prior to competition and, although speculative, there may be more potent clinical manifestations in individuals with below-average baseline function, or those with pre-existing respiratory disorders (e.g., asthma). Respiratory muscle fatigue was most commonly assessed indirectly using maximal static mouth-pressure manoeuvres, and respiratory muscle endurance via maximum voluntary ventilation (MVV₁₂). Objective nerve-stimulation data from one study, and others documenting the time-course of recovery, implicate peripheral neuromuscular factors as the mechanism underpinning such fatigue. Evidence of respiratory muscle fatigue was more prevalent following marathon compared to ultra-marathon, and might be a factor of work rate, and thus exercise ventilation, which is tempered during longer races. Potential implications of respiratory muscle fatigue on health and marathon/ultra-marathon performance have been discussed, and include a diminished postural stability that may increase the risk of injury when running on challenging terrain, and possible respiratory muscle fatigue-induced effects on locomotor limb blood flow. This review provides novel insights that might influence marathon/ultra-marathon preparation strategies, as well as inform medical best-practice of personnel supporting such events.

Lung function and oxygen saturation after participation in Norseman Xtreme Triathlon

OBJECTIVES

To examine evidence of exercise-induced bronchoconstriction (EIB) defined as ≥10% reduction in forced expiratory volume in one second (FEV₁ ) and exercise-induced arterial hypoxemia (EIAH) defined as ≥4% reduction in oxygen saturation (SpO₂ ) from before to after participation in the Norseman Xtreme Triathlon. Secondarily, to assess whether changes in FEV₁ and SpO₂ are related to respiratory symptoms, training volume, and race time.

METHODS

In this quasi-experimental non-controlled study, we included 63 triathletes (50♂/13♀) aged 40.3 (±9.0) years (mean ± SD). Fifty-seven (46♂/11♀) measured lung function and 54 (44♂/10♀) measured SpO₂ before the race, 8-10 minutes after the race (post-test 1) and the day after the race (post-test 2). Respiratory symptoms and training volume were recorded with modified AQUA questionnaire. ANOVA for repeated measures was used to detect differences in lung function and SpO₂ . Statistical significance was accepted at 0.05 level.

RESULTS

Twenty-six participants (46%) presented with EIB at post-test 1 and 16 (28%) at post-test 2. Lung function variables were significantly reduced from baseline to post-test 1 and 2. Thirty-five participants (65%) showed evidence of mild to moderate EIAH. No significant correlations were observed except a weak correlation between maximal reduction in FEV₁ and respiratory symptoms (r = 0.35, P = .016).

CONCLUSION

Our results demonstrated that 46% of the participants presented with EIB and 65% showed evidence of EIAH after the Norseman Xtreme Triathlon. Changes in FEV₁ and SpO₂ were not correlated to weekly training hours or race time. We observed a weak correlation between maximal reduction in FEV₁ and respiratory symptoms.

Effects of caffeine on inspiratory muscle function

Research suggests that caffeine can enhance measures of muscular strength in the upper and lower extremities, although the literature is somewhat equivocal. Little is known on whether or not caffeine will improve maximal inspiratory pressure (MIP), a surrogate measure of inspiratory muscle strength. The purpose of the study was to determine the effects of a moderate dose of caffeine on inspiratory muscle function. Fifteen (8 male, 7 female) healthy adults (mean ± SD: age = 24.3 ± 6.4 years; height = 1.75 ± 0.11 m; body mass = 78.8 ± 16.5 kg) volunteered to participate in the study which used a double-blind, placebo-controlled, cross-over design. During the initial visit, baseline data was collected and participants were familiarized with inspiratory muscle measurements. For the second and third visits, participants ingested either a 5 mg kg^-1 dose of caffeine (CAF) or placebo capsule (PL). After one hour, they completed at least 12 maximal inspiratory manoeuvres with 1 min rest between each attempt. MIP, maximal inspiratory peak pressure (PP), and maximal rate of pressure development (MRPD) were recorded. The CAF trial resulted in significantly higher MIP (154.7 ± 35.8 vs. 146.6 ± 37.6 cmH₂O; p = 0.02) and PP (165.8 ± 36.8 vs. 158.3 cmH₂O; p = 0.01) compared to the PL condition. No significant difference was observed in MRPD (p = 0.18). MIP and PP improved after ingestion of caffeine compared to the placebo condition. The findings from the study further establish caffeine's potential ergogenic benefit on measures of muscular strength.

Physiological and Pathophysiological Consequences of a 25-Day Ultra-Endurance Exercise Challenge

Background: This case-report characterized the respiratory, cardiovascular, and nutritional/gastrointestinal (GI) responses of a trained individual to a novel ultra-endurance exercise challenge.

Case Presentation: A male athlete (age 45 years; V˙O₂max 54.0 mL⋅kg^-1⋅min^-1) summited 100 mountains on foot in 25 consecutive days (all elevations >600 m).

Measures: Laboratory measures of pulmonary function (spirometry, whole-body plethysmography, and single-breath rebreathe), respiratory muscle function (maximum static mouth-pressures), and cardiovascular structure and function (echocardiography, electrocardiography, large vessel ultrasound, and flow-mediated dilatation) were made at baseline and 48 h post-challenge. Dietary intake (four-day food diary), self-reported GI symptoms and plasma endotoxin concentrations were assessed at baseline, pre/post mid-point, pre/post end-point, and 48 h post-challenge.

Results: The challenge was completed in a total exercise time of 142 h (5.3 ± 2.8 h⋅d^-1), with a distance of 1141 km (42.3 ± 43.9 km⋅d^-1), and energy expenditure of 80460 kcal (2980 ± 1451 kcal⋅d^-1). Relative to baseline, there were post-challenge decreases in pulmonary capacities and expiratory flows (≤34%), maximum expiratory mouth-pressure (19%), and maximum voluntary ventilation (29%). Heart rate variability deteriorated, manifesting as a 48% decrease in the root mean square of successive differences and a 70% increase in the low-frequency/high-frequency ratio. Pre- to post-challenge endotoxin concentrations were elevated by 60%, with a maximum increase of 130% after a given stage, congruent with an increased frequency and severity of GI symptoms.

Conclusion: The challenge resulted in pulmonary and autonomic dysfunction, endotoxaemia, and GI distress. The findings extend our understanding of the limits of physiological function and may inform medical best-practice for personnel supporting ultra-endurance events.

Acute Responses of Novel Cardiac Biomarkers to a 24-h Ultra-Marathon

The aim of the present study was to examine the acute effect of an ultra-endurance performance on N-terminal pro-brain natriuretic peptide (NT-proBNP), cardiac specific troponin T (cTnT), creatinine kinase-myocardial band (CK-MB), high sensitive C-reactive protein (hsCRP), ischemia modified albumin (IMA), heart-type fatty acid binding protein (H-FABP) and cardiovascular function. Cardiac biomarkers were evaluated in 14 male ultra-marathoners (age 40 ± 12 years) during a 24 h ultra-marathon at five points (i.e., Pre-race; Marathon, 12-h run, 24-h run, and 48-h post-race). All subjects underwent baseline echocardiography assessment at least 10 days prior to the ultra-marathon and 48 h post-race. The average distance covered during the race was 149.4 ± 33.0 km. Running the ultra-marathon led to a progressive increase in hsCRP and H-FABP concentrations (p < 0.001). CK-MB and cTnT levels were higher after a 24-h run compared to pre-race (p < 0.05). Diastolic function was altered post-race characterized by a reduction in peak early to late diastolic filling (p < 0.01). Running an ultra-marathon significantly stimulates specific cardiac biomarkers; however, the dynamic of secretion of biomarkers linked to myocardium ischemia were differentially regulated during the ultra-marathon race. It is suggested that both exercise duration and intensity play a crucial role in cardiovascular adaptive mechanisms and cause risk of cardiac stress in ultra-marathoners.

Pulmonary and respiratory muscle function in response to 10 marathons in 10 days

PURPOSE

Marathon and ultramarathon provoke respiratory muscle fatigue and pulmonary dysfunction; nevertheless, it is unknown how the respiratory system responds to multiple, consecutive days of endurance exercise.

METHODS

Nine trained individuals (six male) contested 10 marathons in 10 consecutive days. Respiratory muscle strength (maximum static inspiratory and expiratory mouth-pressures), pulmonary function (spirometry), perceptual ratings of respiratory muscle soreness (Visual Analogue Scale), breathlessness (dyspnea, modified Borg CR10 scale), and symptoms of Upper Respiratory Tract Infection (URTI), were assessed before and after marathons on days 1, 4, 7, and 10.

RESULTS

Group mean time for 10 marathons was 276 ± 35 min. Relative to pre-challenge baseline (159 ± 32 cmH₂O), MEP was reduced after day 1 (136 ± 31 cmH₂O, p = 0.017), day 7 (138 ± 42 cmH₂O, p = 0.035), and day 10 (130 ± 41 cmH₂O, p = 0.008). There was no change in pre-marathon MEP across days 1, 4, 7, or 10 (p > 0.05). Pre-marathon forced vital capacity was significantly diminished at day 4 (4.74 ± 1.09 versus 4.56 ± 1.09 L, p = 0.035), remaining below baseline at day 7 (p = 0.045) and day 10 (p = 0.015). There were no changes in FEV₁, FEV₁/FVC, PEF, MIP, or respiratory perceptions during the course of the challenge (p > 0.05). In the 15-day post-challenge period, 5/9 (56%) runners reported symptoms of URTI, relative to 1/9 (11%) pre-challenge.

CONCLUSIONS

Single-stage marathon provokes acute expiratory muscle fatigue which may have implications for health and/or performance, but 10 consecutive days of marathon running does not elicit cumulative (chronic) changes in respiratory function or perceptions of dyspnea. These data allude to the robustness of the healthy respiratory system.

Acute, chronic, and combined pulmonary responses to swimming in competitive swimmers

The combined effects of swimming on the inspiratory muscles and pulmonary functions are not well known. The aim of the present study was to determine the acute, chronic, and combined effects of swimming on the pulmonary functions and respiratory muscles of competitive swimmers. Thirty males (15 in the experimental group [EG] and 15 in the control group [CG]) participated in this study. The EG subjects participated in an 8-week swim training program and performed 1 day before and after an 8-week 100-m swimming event. Pulmonary functions and respiratory muscle strength were measured immediately before and after the swimming event in the EG and before and after an 8-week period in the CG. The obtained data were analyzed using repeated measures one-way analysis of variance, least significant difference, and independent- and paired-sample t-tests. Swimming exerted negative acute effects (p < 0.05) and positive chronic effects (p < 0.05) on respiratory muscle strength and pulmonary functions. Further, the negative acute effects decreased the combined effects of the chronic and acute effects of swimming on respiratory muscle strength and pulmonary functions (p < 0.05). The results indicated that swimming exerts negative acute, positive chronic, and combined effects on respiratory muscle strength and pulmonary functions.

Inspiratory muscle training improves exercise capacity with thoracic load carriage

Thoracic load carriage (LC) exercise impairs exercise performance compared to unloaded exercise, partially due to impaired respiratory mechanics. We investigated the effects of LC on exercise and diaphragmatic fatigue in a constant-load exercise task; and whether inspiratory muscle training (IMT) improved exercise capacity and diaphragmatic fatigue with LC. Twelve recreationally active males completed three separate running trials to exhaustion (Tlim ) at a fixed speed eliciting 70% of their V˙O2max . The first two trials were completed either unloaded (UL) or while carrying a 10 kg backpack (LC). Subjects then completed 6 weeks of either true IMT or placebo-IMT. Posttraining, subjects completed an additional LC trial identical to the pretraining LC trial. Exercise metabolic and ventilatory measures were recorded. Diaphragm fatigue was assessed as the difference between preexercise and postexercise twitch diaphragmatic pressure (Pdi, tw ), assessed by bilateral stimulation of the phrenic nerve with esophageal balloon-tipped catheters measuring intrathoracic pressures. Tlim was significantly shorter (P < 0.001) with LC compared with UL by 42.9 (29.1)% (1626.5 (866.7) sec and 2311.6 (1246.5) sec, respectively). The change in Pdi, tw from pre- to postexercise was significantly greater (P = 0.001) in LC (-13.9 (5.3)%) compared with UL (3.8 (6.5)%). Six weeks of IMT significantly improved Tlim compared to pretraining (P = 0.029, %Δ +29.3 (15.7)% IMT, -8.8 (27.2)% Placebo), but did not alter the magnitude of diaphragmatic fatigue following a run to exhaustion (P > 0.05). Minute ventilation and breathing mechanics were unchanged post-IMT (P > 0.05). Six weeks of flow-resistive IMT improved exercise capacity, but did not mitigate diaphragmatic fatigue following submaximal, constant-load running to volitional exhaustion with LC.

Respiratory muscle strength is decreased after maximal incremental exercise in trained runners and cyclists

The respiratory muscle fatigue seems to be able to limit exercise performance and may influence the determination of maximal oxygen uptake (V̇O_2max) or maximum aerobic work rate during maximal incremental test. The aim of this study was therefore to investigate whether maximal incremental exercise decreases respiratory muscle strength. We hypothesized that respiratory muscle strength (maximal pressure) will decrease after maximal incremental exercise to exhaustion. 36 runners and 23 cyclists completed a maximal incremental test on a treadmill or a cycle ergometer with continuous monitoring of expired gases. Maximal inspiratory (MIP) and expiratory (MEP) pressure measurements were taken at rest and post- exercise. At rest, the MIP and MEP were 140±25 and 172±27 in runners vs. 115±26 and 146±33 in cyclists (p<0.05 between groups, respectively). The rest values of MIP and MEP were correlated to the V̇O_2peak in all athletes, r=0.34, p<0.01 and r=0.36, p<0.01, respectively. At exhaustion, the MIP and MEP decreased significantly post- test by 13±7% and 13±5% in runners vs. 17±11% and 15±10% in cyclists (p>0.05), respectively. Our results suggest that respiratory muscle strength is decreased following maximal incremental exercise in trained runners and cyclists.

Unstable rocker shoes promote recovery from marathon-induced muscle damage in novice runners

We recently reported that wearing unstable rocker shoes (Masai Barefoot Technology: MBT) may enhance recovery from marathon race-induced fatigue. However, this earlier study only utilized a questionnaire. In this study, we evaluated MBT utilizing objective physiological measures of recovery from marathon-induced muscle damages. Twenty-five university student novice runners were divided into two groups. After running a full marathon, one group wore MBT shoes (MBT group), and the control group (CON) wore ordinary shoes daily for 1 week following the race. We measured maximal isometric joint torque, muscle hardness (real time tissue elastography of the strain ratio) in the lower limb muscles before, immediately after, and 1, 3, and 8 days following the marathon. We calculated the magnitude of recovery by observing the difference in each value between the first measurement and the latter measurements. Results showed that isometric torques in knee flexion recovered at the first day after the race in the MBT group while it did not recover even at the eighth day in the CON group. Muscle hardness in the gastrocnemius and vastus lateralis showed enhanced recovery in the MBT group in comparison with the CON group. Also for muscle hardness in the tibialis anterior and biceps femoris, the timing of recovery was delayed in the CON group. In conclusion, wearing MBT shoes enhanced recovery in lower leg and thigh muscles from muscle damage induced by marathon running.

The Effects of a 36-Hour Mixed Task Ultraendurance Race on Mucosal Immunity Markers and Pulmonary Function

OBJECTIVE

The present study was conducted to assess the changes in mucosal immunity and pulmonary function among participants in a 36-hour mixed task ultraendurance race.

METHODS

Thirteen of the 20 race participants volunteered for the investigation (age 34±5 y). The event consisted of a mixture of aerobic, strong man, and military-style exercise. Participants had a pulmonary function test and gave a finger stick capillary blood sample and unstimulated saliva samples both before the event and upon dropout or completion. The blood sample was analyzed for hematocrit, and the saliva sample was analyzed for salivary flow rate, salivary alpha amylase, salivary immunoglobulin A (IgA), and IgA type 1.

RESULTS

Significant differences were noted among the finishers and those who dropped out in salivary flow rate (P = .026), salivary IgA (P = .017), and peak expiratory flow (P = .05) measurements. Salivary flow rate and IgA for the race finishers were reduced from pre- to postrace, whereas the nonfinishers showed no change or small increases. No significant differences emerged for other variables.

CONCLUSIONS

Based on the results of the present investigation, finishing a 36-hour mixed task ultra-endurance event results in a decline in both pulmonary function and mucosal immunity compared with competitors who do not finish.

Aspects of respiratory muscle fatigue in a mountain ultramarathon race

PURPOSE

Ultramarathon running offers a unique possibility to investigate the mechanisms contributing to the limitation of endurance performance. Investigations of locomotor muscle fatigue show that central fatigue is a major contributor to the loss of strength in the lower limbs after an ultramarathon. In addition, respiratory muscle fatigue is known to limit exercise performance, but only limited data are available on changes in respiratory muscle function after ultramarathon running and it is not known whether the observed impairment is caused by peripheral and/or central fatigue.

METHODS

In 22 experienced ultra-trail runners, we assessed respiratory muscle strength, i.e., maximal voluntary inspiratory and expiratory pressures, mouth twitch pressure (n = 16), and voluntary activation (n = 16) using cervical magnetic stimulation, lung function, and maximal voluntary ventilation before and after a 110-km mountain ultramarathon with 5862 m of positive elevation gain.

RESULTS

Both maximal voluntary inspiratory (-16% ± 13%) and expiratory pressures (-21% ± 14%) were significantly reduced after the race. Fatigue of inspiratory muscles likely resulted from substantial peripheral fatigue (reduction in mouth twitch pressure, -19% ± 15%; P < 0.01), as voluntary activation (-3% ± 6%, P = 0.09) only tended to be decreased, suggesting negligible or only mild levels of central fatigue. Forced vital capacity remained unchanged, whereas forced expiratory volume in 1 s, peak inspiratory and expiratory flow rates, and maximal voluntary ventilation were significantly reduced (P < 0.05).

CONCLUSIONS

Ultraendurance running reduces respiratory muscle strength for inspiratory muscles shown to result from significant peripheral muscle fatigue with only little contribution of central fatigue. This is in contrast to findings in locomotor muscles. Whether this difference between muscle groups results from inherent neuromuscular differences, their specific pattern of loading or other reasons remain to be clarified.

Training the inspiratory muscles improves running performance when carrying a 25 kg thoracic load in a backpack

Load carriage (LC) exercise in physically demanding occupations is typically characterised by periods of low-intensity steady-state exercise and short duration, high-intensity exercise while carrying an external mass in a backpack; this form of exercise is also known as LC exercise. This induces inspiratory muscle fatigue and reduces whole-body performance. Accordingly we investigated the effect of inspiratory muscle training (IMT, 50% maximal inspiratory muscle pressure (PImax) twice daily for six week) upon running time-trial performance with thoracic LC. Nineteen healthy males formed a pressure threshold IMT (n = 10) or placebo control group (PLA; n = 9) and performed 60 min LC exercise (6.5 km h(-1)) followed by a 2.4 km running time trial (LCTT) either side of a double-blind six week intervention. Prior to the intervention, PImax was reduced relative to baseline, post-LC and post-LCTT in both groups (pooled data: 13 ± 7% and 16 ± 8%, respectively, p < .05) and similar changes were observed post-PLA. Post-IMT only, resting PImax increased +31% (p < .05) and relative to pre-IMT was greater post-LC (+19%) and post-LCTT (+18%, p < .05), however, the relative reduction in PImax at each time point was unchanged (13 ± 11% and 17 ± 9%, respectively, p > .05). In IMT only, heart rate and perceptual responses were reduced post-LC (p < .05). Time-trial performance was unchanged post-PLA and improved 8 ± 4% after IMT (p < .05). In summary, when wearing a 25 kg backpack, IMT attenuated the cardiovascular and perceptual responses to steady-state exercise and improved high-intensity time-trial performance which we attribute in part to reduced relative work intensity of the inspiratory muscles due to improved inspiratory muscle strength. These findings have real-world implications for occupational contexts.

Changes in lung function during an extreme mountain ultramarathon

This study aimed to assess the effects of an extreme mountain ultramarathon (MUM, 330 km, 24,000 D+) on lung function. Twenty-nine experienced male ultramarathon runners performed longitudinally [before (pre), during (mid), and immediately after (post) a MUM] a battery of pulmonary function tests. The tests included measurements of forced vital capacity, forced expiratory volume in 1 s, peak flow, inspiratory capacity, and maximum voluntary ventilation in 12 s (MVV12). A significant reduction in the running speed was observed (-43.0% between pre-mid and mid-post; P < 0.001). Expiratory function declined significantly at mid (P < 0.05) and at post (P < 0.05). A similar trend was observed for inspiratory function (P < 0.05). MVV12 declined at mid (P < 0.05) and further decreased at post (P < 0.05). Furthermore, there are significant negative correlations between performance time and MVV12 pre-race (R = -0.54, P = 0.02) as well as changes in MVV12 between pre- and post-race (R = -0.53, P = 0.009). It is concluded that during an extreme MUM, a continuous decline in pulmonary function was observed, likely attributable to the high levels of ventilation required during this MUM in a harsh mountainous environment.

The clinical value of peak nasal inspiratory flow, peak oral inspiratory flow, and the nasal patency index

OBJECTIVES/HYPOTHESIS

The aim of this study was to ascertain the most reliable objective measurement for the assessment of nasal patency by investigating the relationship between peak nasal inspiratory flow, peak oral inspiratory flow, and the nasal patency index in relation to the patient's subjective perception regarding nasal obstruction.

STUDY DESIGN

Prospective cohort study.

METHODS

This study included 131 volunteers of both genders, aged 18 years or older, with or without nasal symptoms, who were able to give informed consent, completed the study protocol, and could speak and write Dutch fluently. Peak nasal inspiratory flow and peak oral inspiratory flow were performed and nasal patency index was computed. The results were evaluated and compared with the subjective perception of nasal passage, using the validated Nasal Obstruction Symptom Evaluation scale and visual analog scale for nasal passage.

RESULTS

Our study showed that peak nasal inspiratory flow, nasal patency index and nasal patency visual analog scale correlate with the Nasal Obstruction Symptom Evaluation scale in contrast to peak oral inspiratory flow. Peak nasal inspiratory flow and nasal patency index also showed significant association with the Nasal Obstruction Symptom Evaluation scale after adjustment for confounders.

CONCLUSIONS

Peak nasal inspiratory flow is the most reliable method for the assessment of nasal patency. It is quick, inexpensive, and easy to perform, and correlates significantly with the subjective feeling of nasal obstruction. There is no clinical need to measure peak oral inspiratory flow or to calculate the nasal patency index in the evaluation of nasal patency.

LEVEL OF EVIDENCE

4

Influence of exercise intensity on respiratory muscle fatigue and brachial artery blood flow during cycling exercise

PURPOSE

During high intensity exercise, both respiratory muscle fatigue and cardiovascular reflexes occur; however, it is not known how inactive limb blood flow is influenced. The purpose of this study was to determine the influence of moderate and high exercise intensity on respiratory muscle fatigue and inactive limb muscle and cutaneous blood flow during exercise.

METHODS

Twelve men cycled at 70 and 85 % [Formula: see text] for 20 min. Subjects also performed a second 85 % [Formula: see text] test after ingesting 1,800 mg of N-acetylcysteine (NAC), which has been shown to reduce respiratory muscle fatigue (RMF). Maximum inspiratory pressures (P Imax), brachial artery blood flow (BABF), cutaneous vascular conductance (CVC), and mean arterial pressure were measured at rest and during exercise.

RESULTS

Significant RMF occurred with 85 % [Formula: see text] (P Imax, -12.8 ± 9.8 %), but not with 70 % [Formula: see text] (P Imax, -5.0 ± 5.9 %). BABF and BA vascular conductance were significantly lower at end exercise of the 85 % [Formula: see text] test compared to the 70 % [Formula: see text] test. CVC during exercise was not different (p > 0.05) between trials. With NAC, RMF was reduced (p < 0.05) and BABF was significantly higher (~30 %) compared to 85 % [Formula: see text] (p < 0.05).

CONCLUSIONS

These data suggest that heavy whole-body exercise at 85 % [Formula: see text] leads to RMF, decreases in inactive arm blood flow, and vascular conductance, but not cutaneous blood flow.

Ventilation and respiratory mechanics

During dynamic exercise, the healthy pulmonary system faces several major challenges, including decreases in mixed venous oxygen content and increases in mixed venous carbon dioxide. As such, the ventilatory demand is increased, while the rising cardiac output means that blood will have considerably less time in the pulmonary capillaries to accomplish gas exchange. Blood gas homeostasis must be accomplished by precise regulation of alveolar ventilation via medullary neural networks and sensory reflex mechanisms. It is equally important that cardiovascular and pulmonary system responses to exercise be precisely matched to the increase in metabolic requirements, and that the substantial gas transport needs of both respiratory and locomotor muscles be considered. Our article addresses each of these topics with emphasis on the healthy, young adult exercising in normoxia. We review recent evidence concerning how exercise hyperpnea influences sympathetic vasoconstrictor outflow and the effect this might have on the ability to perform muscular work. We also review sex-based differences in lung mechanics.

Diagnosis and management of chronic lung disease in deployed military personnel

Military personnel are a unique group of individuals referred to the pulmonary physician for evaluation. Despite accession standards that limit entrance into the military for individuals with various pre-existing lung diseases, the most common disorders found in the general population such as asthma and chronic obstructive pulmonary disease remain frequently diagnosed. Military personnel generally tend to be a more physically fit population who are required to exercise on a regular basis and as such may have earlier presentations of disease than their civilian counterparts. Exertional dyspnea is a common complaint; establishing a diagnosis may be challenging given the subtle nature of symptoms and lack of specificity with pulmonary function testing. The conflicts over the past 10 years in Iraq and Afghanistan have also given rise to new challenges for deployed military. Various respiratory hazards in the deployed environment include suspended geologic dusts, burn pits, vehicle exhaust emissions, industrial air pollution, and isolated exposure incidents and may give rise to both acute respiratory symptoms and chronic lung disease. In the evaluation of deployed military personnel, establishing the presence of actual pulmonary disease and the relationship of existing disease to deployment is an ongoing issue to both military and civilian physicians. This paper reviews the current evidence for chronic lung disease in the deployed military population and addresses any differences in diagnosis and management.